The present invention relates to laser drilling systems, and more particularly, to a method for aligning a workpiece in a laser drilling system
Material ablation by pulsed light sources has been studied since the invention of the laser. Reports in 1982 of polymers having been etched by ultraviolet (UV) excimer laser radiation stimulated widespread investigations of the process for micromachining. Since then, scientific and industrial research in this field has proliferatedxe2x80x94mostly spurred by the remarkably small features that can be drilled, milled, and replicated through the use of lasers.
Ultrafast lasers generate intense laser pulses with durations from roughly 10xe2x88x9211 seconds (10 picoseconds) to 10xe2x88x9214 seconds (10 femtoseconds). Short pulse lasers generate intense laser pulses with durations from roughly 10xe2x88x9210 seconds (100 picoseconds) to 10xe2x88x9211 seconds (10 picoseconds). A wide variety of potential applications for ultrafast and short pulse lasers in medicine, chemistry, and communications are being developed and implemented. These lasers are also a useful tool for milling or drilling holes in a wide range of materials. Hole sizes as small as a few microns, even sub-microns, can readily be drilled. High aspect ratio holes can be drilled in hard materials, such as cooling channels in turbine blades, nozzles in ink-jet printers, or via holes in printed circuit boards.
Optical parallel processing of laser-milled holes is key to increasing the throughput of, and the profitability of laser micromachining. Beamsplitting devices such as diffractive optical elements (DOEs) are currently used in laser micromachining to divide a single beam into multiple beams to allow for parallel processing of the workpiece (material to be drilled). Hole geometry requirements, and the ability to produce consistent, repeatable results are critical to individual manufacturing applications. In inkjet nozzle hole drilling using laser micromachining, the consistency and repeatability of the nozzle holes translate to consistent print quality and acceptable print resolution.
Alignment of the workpiece is an important step to ensure that an entire multiple-hole pattern can be drilled at precisely the location required by design specifications. While alignment is less of an issue for a single hole to be drilled, it is much more important, and more difficult to accomplish with a multiple-hole pattern. What is needed is a way to improve accuracy of workpiece alignment in a parallel process laser drilling system.
In accordance with the present invention, a method is provided for aligning a workpiece in a laser drilling system. The method includes: determining position data for two or more target alignment markers residing on a movable workpiece holder, where the target alignment markers are defined in relation a drilling pattern for the workpiece and indicate a target workpiece position; placing a workpiece on the movable workpiece holder; measuring position data for alignment markers associated with the workpiece, thereby determining an actual workpiece position; and computing a translation angle between the actual workpiece position and the target workpiece position simultaneously with computing a translation distance between the actual workpiece position and the target workpiece position. The method may further include adjusting the workpiece based on the computed translation angle and translation distance, thereby aligning the workpiece in the laser drilling system.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.